General Settings
Open the settings window by clicking the gear icon in the sidebar or going to Settings.
Theme
Choose between Light and Dark themes. The interface updates immediately when you switch. When dark mode is active, windows open with a dark background from the very first frame -- no white flash.
Language
MailCopilot supports 6 interface languages:
- English
- Russian
- French
- German
- Spanish
- Italian
Select your preferred language from the dropdown. The interface switches instantly without needing a restart.
Message Retention
Controls how long full message copies (HTML content, inline images, and attachments) are kept on disk. Open Settings > General and use the Keep full message copy for dropdown to choose a retention period. Older messages remain searchable through their headers and plain text — only the rich .eml file is deleted when the period expires.
| Option | Duration |
|---|---|
| 30 days | ~1 month |
| 90 days | ~3 months |
| 180 days | ~6 months |
| 1 year | 365 days (default) |
| Forever | No automatic pruning |
When you shorten the retention period, MailCopilot shows a preview of how many cached messages will be removed before applying the change. Messages on the server are never modified -- only the local copy is affected.
Default Email Application
Toggle whether MailCopilot is registered with your operating system as the default handler for mailto: links. When enabled, clicking a "Send email" link in your browser, terminal, or another desktop application opens the MailCopilot compose window with the recipient and any other parameters pre-filled (to, cc, bcc, subject, body).
Registration is opt-in -- MailCopilot does not claim the protocol unless you explicitly enable this toggle. On Linux the registration goes through the desktop file's MimeType declaration; on macOS through open-url; on Windows through the protocol entry under HKCR\mailto. You can revert at any time by toggling this off, or by changing the default email handler in your system settings.
When MailCopilot is launched a second time -- for example by clicking a mailto: link while the app is already open -- the existing window is brought to the front instead of opening a duplicate, so you only ever have one running instance.
TLS Certificate Pinning
TLS Certificate Pinning adds an extra layer of security for your email connections. It ensures that your client only connects to servers presenting a specific certificate, protecting against man-in-the-middle attacks.
Managing Certificate Pins
- Open Settings and go to the Accounts section.
- Click Edit on an account to open its settings.
- Scroll down to the TLS Certificate Pinning section.
The section shows a table of pinned certificates with their host, port, fingerprint, and the date they were added.
Adding a Pin
- Click Add Pin.
- Enter the host (e.g.,
imap.gmail.com) and port (e.g.,993). - Click Fetch & Pin. MailCopilot connects to the server, retrieves its certificate, and shows you the fingerprint.
- Confirm to save the pin.
Removing a Pin
Click the delete button next to any pin in the table to remove it. After removing a pin, MailCopilot will accept any valid certificate from that server.
When you add or remove a pin, MailCopilot automatically reconnects to the mail server so the change takes effect immediately.
When to Use Certificate Pinning
Certificate pinning is especially useful for corporate environments or situations where you need to verify that your email connections are going to the expected servers. For most personal use, the default TLS verification is sufficient.